Breeding systems determine how individuals get together to reproduce, and influence the amount of genetic diversity in populations and the potential for speciation. Plants provide model systems for understanding factors promoting changes in breeding systems because of their variability in reproductive systems. In heterostyly, distinctive floral forms are associated with chemical incompatibilities that usually prevent mating between similar forms and promote crossing between forms (outcrossing). Oxalis alpina appears to be evolving a new breeding system, with loss of one floral morph in some populations. To test previous models indicating that changes in self-incompatibility are responsible for breeding system evolution, crosses will be carried out to determine whether changes in incompatibility are more common in populations where heterostyly is more highly modified. Outcrossing rates will be measured because greater self-compatibility could retard loss of morphs. The relative fitness of offspring from crosses within and between different morphs will be measured to understand the importance of inbreeding depression in this breeding system change. Research will focus on populations of Oxalis alpina occurring in mountain ranges extending through Mexico, Arizona, and New Mexico.
This research provides insights into evolutionary factors that underlie modifications of plant breeding systems, and reproductive systems in general. The research fosters an international collaboration, with participation of faculty, graduate students, and undergraduates from U.S. and Mexican institutions. This project is being supported by the Office of International Science and Engineering.
